Analysis: This question examines the six organs and functions of plants, and answers the questions accordingly.

A complete green flowering plant consists of six organs: root, stem, leaf, flower, fruit and seed. The water and inorganic salts absorbed by the root are transported from the stem to the leaves and other places for the use of the plant, and the leaves can also be used for photosynthesis to synthesize organic matter. It can be seen that the roots, stems and leaves of the plant are related to nutrients, so they belong to the vegetative organs. After the flowers are opened, they are pollinated and fertilized to produce fruits and seeds, and then the seeds are used to breed offspring, so the flowers.

The edible part of lotus root is rhizome, which belongs to stem; Celery is mainly stem; Yam is an underground stem and also belongs to the stem; All belong to vegetative organs. Soybeans are seeds and belong to reproductive organs.

So choose: C.

Comments: Mastering the six organs of plants, understanding their functions, and distinguishing reproductive organs from vegetative organs will soon make a correct choice.